The present invention is directed toward disc brakes, and more particularly toward a pad wear compensator for a disc brake caliper.
Disc brakes are being included on more and more bicycles as consumers are ever increasingly demonstrating a preference for disc brakes over conventional rim brakes such as caliper brakes, cantilever brakes and side pull cantilever brakes. While both mechanical and hydraulic disc brakes have been available for bicycles for many years, only recently have there been advances in disc brake caliper design that have made disc brakes sufficiently lightweight, reliable and inexpensive to satisfy consumer preferences. While more efficient and powerful caliper drive mechanisms are evolving, to date manufacturers of disc brakes have not adequately addressed consumer need for ease of adjustment and maintenance of these caliper brakes. One area of particular concern is structures for compensating for pad wear.
One known pad wear compensator provides a set screw that can be advanced within a caliper housing to advance an operatively associated brake pad as the pad wears. The set screw resides within a threaded bore in the housing and requires a turning tool such as a hex wrench to advance the pad. In addition, to lock the pad in a select position, a second locking screw is threadably engaged in the bore to lock the adjustment screw in place. This structure, while allowing for advancement of the pad to compensate for pad wear, is extremely cumbersome to use, requiring the removal of one screw and the turning of two screws as well as the use of a separate tool to make an adjustment. In addition, because the adjustment screw resides within the threaded bore, there is no reliable way to gauge how far the pad has been extended so as to assess remaining pad life. Furthermore, the structure fails to provide any indexing to insure select axial advancement of the brake pad as the adjustment screw is rotated.
Another known pad wear compensator provides a knob which can be rotated to advance the caliper housing relative to a disc operatively associated with the housing so as to compensate for brake pad wear. While this structure overcomes some of the complexity and tool requirements of the structure discussed in the preceding paragraph, it still has numerous deficiencies. Most notably, by providing for advancement of the entire housing relative to the disc as opposed to simply advancement of the pad itself relative to the housing and the disc as it wears, the advancement structure must reside outside of the housing and is thus subject to damage and abuse in use. In addition, while this structure does allow for observation of how far the housing has been advanced relative to the disc, it does not provide a reliable indication of pad wear, as adjustment of the housing may be dictated by other factors such as disc alignment.
Yet another known pad wear compensator provides a knob which threadably engages a caliper housing. The knob can be rotated relative to the caliper housing and thus advanced and retracted axially of the housing. As the knob is rotated to advance it relative to the housing it also advances a pad actuation mechanism along with a pad assembly associated therewith to advance the pad assembly. The opposing pad is fixed against movement relative to the housing. However, the housing itself is moveable relative to a disc so that by movement of the caliper housing and movement of the pad wear compensation knob, pad wear on each of the pads can be compensated for. This structure is still very cumbersome in that only one pad can be advanced relative to the housing. In addition, the knob both rotates and is advanced relative to the housing, providing a potential avenue for grit and other contaminates to effect smooth operation of the caliper actuation mechanism. Finally, because the housing itself is moveable relative to the disc to enable compensation of the fixed pad, there is no reliable indication of how much wear the respective pads have experienced.
The present invention is intended to overcome one or more of the problems discussed above.
A disc brake caliper includes a housing containing a pair of opposing brake pad assemblies configured to reside on opposite sides of a disc operatively associated therewith. At least one of the brake pad assemblies is advanced and retracted relative to the disc by a drive mechanism along an advancement axis to effect braking. A pad wear compensation apparatus is operatively associated with at least one of the brake pad assemblies to advance the brake pad assembly along the advancement axis as it wears. The pad wear compensation apparatus includes an adjustment knob attached to the housing for rotation about a rotation axis and fixed against axial movement. A rotary to linear linkage between the at least one brake pad assembly and the knob provides axial advancement of the brake pad assembly relative to the housing upon axial rotation of the knob in a select direction. The pad wear compensation apparatus preferably further includes in indicator visually observable outside the housing. The indicator is operatively associated with the rotary to linear linkage to advance with the brake pad assembly as the adjustment knob is rotated in a select direction. The rotary to linear linkage preferably includes the indicator. The indicator has a leading portion and a trailing portion extending into an orifice on the knob along the rotation axis. The trailing portion of the indicator and the orifice are configured to permit axial movement of the indicator relative to the knob but to prevent radial movement of the indicator relative to the knob so that as the knob is rotated about the rotation axis the indicator is rotated about the rotation axis. The leading portion of the indicator preferably has threads which engage complimentary threads within the housing that are fixed against radial movement relative to the indicator and fixed against movement along the advancement axis relative to the brake pad assembly. Thus, as the knob is rotated in the select direction, the indicator is advanced along the advancement axis relative to the housing. A link is provided between the indicator and the brake pad so that as the indicator is advanced along the advancement axis the brake pad assembly is advanced. A tactile indicator may be associated with the knob for providing a tactile indication of advancement of the brake pad assembly along the advancement axis a select amount as the knob is rotated in the select direction. The tactile indicator preferably includes index knurls within the housing that are fixed against rotation relative to the knob and complimentary detents operatively associated with the knob engaging the knurls as the knob is rotated relative to the detents.
A second aspect of the invention is a mechanical disc brake caliper including a caliper housing. First and second brake pad assemblies each having a leading brake pad reside within the housing on opposite sides of a disc operatively associated with the caliper. A drive within the housing is operatively associated with the first brake pad assembly for advancing and retracting the first brake pad assembly relative to the disc along an advancement axis to effect braking by advancing the leading brake pad into contact with the disc. A pad wear compensation apparatus is operatively associated with the first brake pad assembly to advance the brake pad assembly along the advancement axis as the brake pad wears. The pad wear compensation apparatus includes an adjustment knob attached to the housing for rotation about a rotation axis. An indicator has a leading portion within the housing and a trailing portion engaging the knob along the rotation axis. The trailing portion and the knob are configured to permit axial movement of the indicator relative to the knob but to prevent rotational movement of the indicator relative to the knob so that as the knob is rotated about the rotation axis the indicator is rotated about the rotation axis. Threads on the leading portion of the indicator engage complimentary threads attached to the drive that are fixed against radial movement relative to the indicator and fixed against movement along the advancement axis relative to the drive. Thus, as the knob is rotated in a select direction, the indicator is advanced along the advancement axis relative to the drive. A link between the indicator and the first brake pad assembly advances the first brake pad assembly along the advancement axis as the indicator is advanced. The knob preferably has an orifice that extends through the knob along the rotation axis and the distal end of the indicator is axially received therein. The orifice and the distal end of the indicator are configured to allow axial movement of the distal end within the orifice but to prevent rotational movement of the distal end relative to the knob. The distal end of the indicator is visibly observable through the orifice to provide a visual indication of how far the pad assembly is advanced. Preferably a tactile indicator is operatively associated with the knob for providing a tactile indication of advancement of the brake pad assembly along the advancement axis a select amount as the knob is rotated in the select direction.
Yet another aspect of the present invention is a pad wear compensation apparatus for a disc brake caliper. The disc brake caliper has a housing containing a pair of opposing brake pad assemblies configured to reside on opposite sides of a disc operatively associated with the caliper housing. At least one brake pad assembly is advanced and retracted relative to the disc along an advancement axis by a drive to effect braking. The pad wear compensation apparatus is operatively associated with at least one brake pad assembly to advance the brake pad along the advancement axis as it wears. The pad wear compensation apparatus includes an adjustment member attached to the housing for rotation about a rotation axis. A rotary to linear linkage between the at least one brake pad assembly and the adjustment member provides for axial advancement of the brake pad assembly relative to the housing upon axial rotation of the knob in a select direction. An indicator is associated with the knob for providing a tactile indication of advancement of the pad assembly along the advancement axis a select amount as the knob is rotated in the select direction. The tactile indicator preferably includes indexing knurls within the housing that are fixed against rotation relative to the adjustment member and complimentary detents operatively associated with the adjustment member which engage the knurls as the knob is rotated relative to the detents. The adjustment member may be fixed against axial movement relative to the housing.
Another aspect of the present invention is a method for attaching a disc brake caliper of a bicycle disc brake to a bicycle frame. The caliper has a caliper housing and a pair of brake pads within the housing positioned to receive a planer disc brake operatively associated with the caliper between the pair of brake pads. A drive advances at least one of the brake pads into contact with the disc along an advancement axis. The method includes providing a pad wear compensator within the housing for advancing and retracting the pads along the advancement axis relative to the housing. An attachment structure is also provided between the caliper housing and the bicycle frame allowing for infinite variation in the angle of incidence between the advancement axis and the plane of the disc. The pads are advanced relative to the housing into flush contact with the disc by using the pad wear compensation apparatus. With the pads advanced into flush contact with the disc, the housing is secured to the frame to prevent movement of the caliper housing relative to the frame. Thereafter, the pads are retracted using the pad wear compensation apparatus a select distance from the disc to allow for free rotation of the disc between the pads.
The pad wear compensation apparatus of the present invention allows for quick and easy advancement of the brake pads relative to the housing to compensate for brake pad wear. The knobs allow for this adjustment to be made without tools, allowing the adjustment to be made anywhere and at any time with minimal effort by the user. Because the knobs rotate but do not advance axially with the remainder of the pad wear compensation apparatus, the opportunity for grit or the like contaminating the apparatus is minimized. The tactile indicator of the pad wear compensation apparatus gives immediate tactile feedback to a user to indicate a select distance of pad advancement for a select increment of rotation of the knob. The pad wear compensation apparatus also includes a visual indicator giving an immediate visual indication to the user of how far the brake pad has been advanced relative to the housing. In this manner a user can continuously monitor the amount of pad wear left so as to minimize the possibility of excessive pad wear during an extended ride which could cause scoring and ultimately the ruining of an associated disc. Finally, the pad wear compensation apparatus enables a fast and reliable method for attaching a caliper housing to a bicycle frame in proper alignment with a disc. All these many advantages are provided by the pad wear compensation apparatus that consists of simple mechanical elements that can be produced and assembled inexpensively and which provide highly reliable and convenient adjustment.